Reaction: (1) (–)-menthone + NADP+ = (+)-pulegone + NADPH + H+
(2) (+)-isomenthone + NADP+ = (+)-pulegone + NADPH + H+
For diagram of reaction click here.
Systematic name: (–)-menthone:NADP+ oxidoreductase
Comments: NADH cannot replace NADPH as reductant. The Δ8,9-double bond of (+)-cis-isopulegone and the Δ1,2-double bond of (±)-piperitone are not substrates. The enzyme from peppermint (Mentha x piperita) converts (+)-pulegone into both (–)-menthone and (+)-isomenthone at a ratio of 70:30 for native enzyme but it does not catalyse the reverse reaction. This enzyme is a member of the medium-chain dehydrogenase/reductase superfamily.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Ringer, K.L., McConkey, M.E., Davis, E.M., Rushing, G.W. and Croteau, R. Monoterpene double-bond reductases of the (–)-menthol biosynthetic pathway: isolation and characterization of cDNAs encoding (–)-isopiperitenone reductase and (+)-pulegone reductase of peppermint. Arch. Biochem. Biophys. 418 (2003) 80-92. [PMID: 13679086]